Typically the knife assembly on harvest headers comprises a knife extending along the front lower edge of the header table, the knife comprising a plurality of triangular knife sections attached to a knife bar such that the apex of the triangle extends forward from the knife bar. The exposed side edges of the knife sections are sharpened. Guards are attached to the front lower edge of the header table and serve to protect the knife sections from breakage when contacting stones and like obstructions. The guards comprise pointed guard fingers extending forward, and the knife moves back and forth along the edge of the header table with the knife sections moving in a slot cut laterally through the guard fingers. In addition to protecting the knife, the guard fingers also enable the knife sections to cut the crop. As the knife section moves back and forth it pushes crop against the sides of those portions of the guard finger that are above and below the slot, shearing the crop stalks.
In regions where the growing season is too short to permit two separate crops one after the other, inter-seeded cropping may be practiced where the second crop is seeded into the first one before the first crop is harvested. For example it is known to plant soybeans in the spring into an established field of winter wheat that was seeded the previous fall. The soybeans and wheat grow side by side and when the wheat is mature it is harvested, typically with a harvest header as described above. Depending on the height of the wheat and the soybeans, significant damage to the soybeans can occur. Where the wheat crop is standing healthy and tall the header can be operated quite high, such that very little of the soybeans is contacted and cut by the knife. Where the wheat crop is short or lying down a significant portion of the soybean plants may be cut off, which often reduces the eventual yield of soybeans.